<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        function add ([a,b]) {
            console.log(a+b);
        }
        add([3,5]);

        let arr = [[1,2,3,4], [5,6,7,8]];
        arr.map(function([item1, item2, it3, it4]) {
            console.log(item1, it3);
        })

        function showAdd(a, b=10) {
            console.log(a+b);
        }
        showAdd(2)
    </script>
</body>
</html>